1. Field of the Invention
The present invention relates to a sheet detecting apparatus and an image forming apparatus.
2. Description of the Related Art
Conventionally, as a method for confirming a conveyance position of a recording medium (sheet) in an apparatus, the recording medium, which is being conveyed, directly contacts and swings a sensor flag arranged in a conveyance path. Positional information of the recording medium is thereby detected from ON/OFF signal information of a sensor such as a photo interrupter. Such a method is generally known.
In such a contact-type sensing configuration, when the swung sensor flag returns to a standby position (hereinafter referred to as “a home position”), the sensor flag collides with an opposed positioning member. This may generate a harsh collision noise or a detection error caused by erroneous detection of the sensor due to bounce of the sensor flag, that is, chattering.
Also, by inclining the abutting surface of the sensor flag as in U.S. Pat. No. 5,923,140, or by forming the cross section of the receiving surface 501a with which the positioning abutting portion 1d of the sensor flag 1 collides, in a V shape as illustrated in FIGS. 13A and 13B, the chattering is reduced, and the detection error is improved. However, in the former case the inclined abutting surface of the sensor flag still abuts on the positioning member. And in the latter case illustrated in FIGS. 13A and 13B, the positioning abutting portion 1d of the sensor flag 1 collides with two inclined surfaces forming the cross-sectional V shape of the receiving surface 501a. Thus, kinetic energy of the sensor flag is converted into sound energy precipitously and is radiated outside as a collision noise, which generates an aurally harsh noise.
Also, in Japanese Patent Laid-Open No. 2007-297190, a sheet detecting lever has an abutting surface. After a sheet material passes, the sheet detecting lever is brought back from a retracting position while the sheet material is passing to an original position. At this time, the abutting surface abuts on another member to return to the original position. When the abutting surface of the sheet detecting lever slides in contact with the another member, the sheet detecting lever moves in an axial direction of the sheet detecting lever. A spring applies a force to the sheet detecting lever in an axial direction so that the abutting surface of the sheet detecting lever and the another member contact with each other at any time. Therefore the sheet detecting lever is hard to move.
The present invention reduces chattering of a sensor flag at a home position and alleviates a collision noise of the sensor flag with a simple configuration.